1. Field of the Invention
The present invention relates to the improvement of a linear bearing for heavy load use suitably utilized for the bearing of a rolling mill or the like where a heavy load is to be applied, for example.
2. Related Background Art
As a conventional linear bearing of the kind for heavy load use, there have been known those disclosed in the specifications of British Patent No. 519,866, U.S. Pat. No. 3,353,876 among others. As a typical example, a bearing shown in FIG. 6 is known, for example. Generally, these bearings are such that as rolling elements, steel balls 3 are inserted between an outer cylinder 1 and an inner cylinder 2. On an inner surface 1a of the outer cylinder 1, a plurality of grooves 4 are formed extendedly in the axial direction with the curved surface having the same radius of curvature r dimensioned equally to the radius r of the steel balls 3. Also, on the surface 2a of the outer diameter of the inner cylinder 2, the grooves 5 having the curved surface of the radius of curvature r dimensioned equally to the radius r of the steel balls 3 are formed corresponding to the grooves 4 of the outer cylinder, respectively.
However, in the conventional linear bearings for heavy load use described above, it is required to precisely coincide the phase of the grooves 4 of the outer cylinder with the phase of the grooves 5 of the inner cylinder. Therefore, it is extremely difficult to machine them.
Also, each surface of the grooves 4 and 5 and the steel balls 3 constitute point contacts. As a result, when a heavy load is applied, the contact surface pressure becomes extremely great. A problem is thus encountered that the grooved surface may be damaged by such as the peeling off, cracking, and others.